CHARACTERIZATION OF THE DIFFERENT STATES OF MYOGLOBIN IN PORK USING COLOR PARAMETERS AND REFLECTANCE RATIOS

Because color is becoming more important to the food industry, color studies are being conducted to improve the control of both raw materials and processes. Several studies have pointed to the importance of the different states of myoglobin in determining the color changes which take place during processing. The aim of this study was to characterize the color parameters (CIE LAB coordinates, reflectance spectrum and reflectance ratios) of the three myoglobin forms (deoxymyoglobin, oxymyoglobin and metmyoglobin) in pork Subscapularis muscle. The deoxymyoglobin present in fresh pork lean meat was converted into the pure states, and color parameters (lightness, redness, yellowness, hue, chroma and a*/b* ratio), reflectance spectrum (400–700 nm) and reflectance ratios (R560/R500, R650/R570, R630/R580 and R630-R580) were obtained. All the color parameters and reflectance ratios (except redness values) varied according to the state of the myoglobin.     

EFFECTS OF INJECTION OF A DILUTE PHOSPHATE-SALT SOLUTION ON PORK CHARACTERISTICS FROM PSE, NORMAL AND DFD CARCASSES

Phosphate-salt pump effects were evaluated on sensory characteristics of pale, soft, exudative (PSE) pork, normal and dark, firm and dry (DFD) pork. Water-holding capacity, instrumental color (L*, a*, b*), pH, and muscle color scores were determined at 24 h postmortem on pork loin pairs (n=21 pairs). Based on color score, paired loins were assigned to PSE, normal or dark, firm, dry groups. PSE muscles were lighter, redder and more yellow than normal or DFD muscles; hue angle indicated that DFD muscles were actually closer to the true red axis of the CIE Lab Color Space. Drip and purge losses were higher (p<0.05) in PSE muscles. Paired loins were pumped with water (controls) or 0.3% tripolyphosphate solution (0.25% salt) to 110% of original weight, vacuum packaged, frozen, cut into chops, and cooked to 70 or 80C. Phosphate-salt pumped loins were juicier and more tender (p<0.05) than water-pumped loins regardless of muscle condition. Loins cooked to 70C were juicier, were more tender (sensory) but required more force to shear than those cooked to 80C.     

SODIUM LACTATE/SODIUM POLYPHOSPHATE EFFECTS ON OXIDATION IN PRECOOKED FROZEN PORK PATTIES

The objective of this study was to evaluate sodium lactate (SL; 0, 1, 2 or 3%) and sodium polyphosphate (SP; 0, 0.1, 0.2 or 0.3%) effects on lipid oxidation and color characteristics of precooked pork patties during frozen storage. Ground pork was mixed with SL and/or SP, stuffed, frozen, sliced and cooked from the frozen state, packaged and held frozen for 14 weeks. Samples containing SP had lower TBARS, regardless of SL content. SL decreased pH, a* and b* values and red color (R630–R580). L* value, hue angle, pork flavor, saltiness, and juiciness increased as SL increased. A moderate correlation occurred between SL and TBARS. SP decreased hue angle, cook loss, and rancid flavor and increased pH, b* value, pork flavor, saltiness, and juiciness. Storage time decreased a* value, red color and juiciness, while saltiness, alkalinity, and rancid flavor scores increased. Based on both physical and sensory characteristics, optimum combinations appear to be 3% SL and 0.2–0.3% SP.     

PSE(白肌)、RFN(正常)、DFD(黑干)3种质量猪肉冷藏期间的肉色稳定性

比较了PSE(白肌)、RFN(正常)、DFD(黑干)3种质量猪肉冷藏期间的肉色稳定性。宰后24h直接切块取样的3种质量猪肉(背最长肌)于(2±1)℃下避光透氧包装[O2透过率=2.06×10-3mL/(m2.h.Pa)]冷藏6d,采用色度计法测定了样品表面L*(亮度)值、a*(红色度)值、b*(黄色度)值、hueangle(色调角)值。从上述指标的变化研究了3种质量猪肉表面的肉色稳定性。3种质量猪肉表面肉色稳定性顺序为:DFD>RFN>PSE;a*值下降、hueangle值上升可反映肉色稳定性变差。     

RELATIONSHIP BETWEEN INSTRUMENTAL AND VISUAL COLOR IN A RAW, FRESH BEEF AND CHICKEN MODEL SYSTEM

A range of meat redness was created by mixing fresh, chilled ground chicken breast and ground beef in predetermined ratios. Samples were scored for visual redness under halogen (incandescent) and cool white fluorescent lighting. Instrumental color characteristics (L*, a*, b*, hue angle, chroma; illuminants A and F) and red color contributed by oxymyoglobin (percentage reflectance at 630 nm versus 580 nm) were determined. Correlation coefficients were determined between visual and instrumental evaluations. The a*, b*, and ΔR (630–580) were highly correlated to visual redness (halogen light: r = 0.99, -0.99, and 0.96, respectively; cool white fluorescent light: 0.98, -0.98, and 0.96, respectively). Regression analysis was conducted to develop equations to predict visual redness using instrumental color measures. In the 20% to 85% beef range, the regression curves were principally linear although the overall relationships (0–100% beef range) were cubic. Among the instrumental color parameters, a*, hue angle, and ΔR (630–580) could be used to predict visual redness for this model system.     

Effect of ionizing radiation on quality characteristics of vacuum-packaged normal,pale–soft–exudative,and dark–firm–dry pork

Normal, pale–soft–exudative (PSE), and dark–firm–dry (DFD) pork Longissimus dorsi muscles were vacuum-packaged, irradiated at 0, 2.5 or 4.5 kGy, and stored at 4 °C for 10 days. The pH, color and lipid oxidation of pork were determined at 0, 5 and 10 days of storage. Volatile production from pork loins was determined at Day 0 and Day 10, and sensory characteristics at Day 7 of storage. Irradiation increased the redness of vacuum-packaged normal, PSE and DFD pork. However, the 2-thiobarbituric acid reactive substances (TBARS) values of three types of pork were not influenced by irradiation and storage time. Irradiation increased the production of sulfur (S)-containing volatile compounds, such as mercaptomethane, dimethyl sulfide, carbon disulfide, methyl thioacetate, and dimethyl disulfide, as well as total volatiles in all three types of pork. Normal pork produced higher levels of total and S-containing volatile compounds than the PSE and DFD pork did. The volatiles produced by irradiation were retained in the vacuum packaging bag during storage. Although the odor preference for the three meat types of pork was not different, the panelists could distinguish irradiated meat from the non-irradiated. Industrial relevance: Several US meat companies have already started test-marketing irradiated meat products. Irradiation and the subsequent storage of pork improved the color of PSE and DFD pork, and showed generally similar effects on the production of volatiles, except that there appeared to be a lower level of S-volatiles in the PSE than in the other two samples. This indicated that irradiation can increase the utilization of low-quality pork (PSE and DFD). DFD pork, in particular, which has shorter shelf-life than the others, could benefit the most from irradiation because the shelf-life of DFD meat can be extended significantly by both the methods of vacuum packaging and irradiation.     

Lipid Oxidation, Color, Volatiles, and Sensory Characteristics of Aerobically Packaged and Irradiated Pork with Different Ultimate pH

ABSTRACT: Irradiation and storage increased lipid oxidation of normal and pale-soft-exudative (PSE) muscles, whereas dark-firm-dry (DFD) muscle was very stable and resistant to oxidative changes. Irradiation increased redness regardless of pork-quality type, and the increases were proportional to irradiation dose. Irradiation increased the production of sulfur-containing volatiles, but not lipid oxidation products. The total volatiles produced in normal and PSE pork were higher than the DFD pork. Some volatiles produced in meat by irradiation evaporated during storage under aerobic packaging conditions. Nonirradiated normal and DFD pork had higher odor preference scores than the nonirradiated PSE, but irradiation reduced the preference scores of all 3 pork-quality types.     

TOCOPHEROL EFFECTS ON FROZEN GROUND PORK COLOR

To assess the effects of α-tocopherol addition on lipid and pigment oxidation of ground pork, 10, 100 or 1000 ppm was added directly in a food grade carrier (2% medium chain triglyceride oil) then pork was overwrapped with polyvinyl-chloride (PVC) film and frozen (-34C) for seven months. Storage time increased extracted deoxymyoglobin percentage, metmyoglobin percentage determined by reflectance spectrophotometry, TBARS, hue angle, and pH, and decreased extracted oxymyoglobin percentage, L*, a* and b* values, and instrumental red color (% reflectance at 630 nm - % reflectance at 580 nm). Extracted metmyoglobin percentage increased through 140 days then decreased through 196 days. Alpha tocopherol increased deoxymyoglobin and decreased oxymyoglobin (extracted) expressed as a percentage of the total pigment, when compared with control samples. Metmyoglobin percentage (reflectance was highest in 10 ppm samples and lowest in 1000 ppm samples. Hue angle and total color were best correlated with other measures of red color.     

CONSUMER EVALUATION OF PORK APPEARANCE WITH DIFFERING PHYSIOLOGICAL AND PACKAGING CONDITIONS

Consumers (n = 116) evaluated color (pink intensity), appearance (wet/dry), overall acceptability and purchase intent of normal, PSE and DFD pork loin slices in PVC and in vacuum packages. Packaging x muscle condition affected (p < 0.05) appearance, overall acceptability and consumer purchase intent of pork slices. Color differences were perceptible to consumers between packaging treatments. PVC-packaged pork was pinker than vacuum-packaged pork. Vacuum-packaged, PSE pork appeared drier than PVC-packaged PSE pork. Normal pork was more acceptable than PSE pork regardless of packaging. DFD pork acceptability was not different from that of normal pork when vacuum packaged. In general purchase intent paralleled consumer evaluation of overall acceptability. Instrumental color data and pH for samples evaluated are also presented.     

Consumer-rated Quality Characteristics as Related to Purchase Intent of Fresh Pork

Consumers (n=556) rated pink color, wet/dry appearance, overall acceptability and purchase intent of normal, pale, soft and exudative (PSE), and dark, firm and dry (DFD) pork loin slices in PVC packages in five retail supermarkets. DFD samples appeared driest and PSE samples appeared wettest. Samples in the higher ranked two purchase intent categories appeared more wet than those in the lower three categories. The pinker PSE samples and all DFD samples were in the higher ranked purchase intent categories. Purchase intent generally paralleled overall acceptability; however, prediction equations indicated that wet/dry appearance, color and overall acceptability all contributed to purchase intent decision depending on muscle condition.     

Metmyoglobin Reducing Capacity of Fresh Normal, PSE, and DFD Pork During Retail Display

Fresh pale, soft, exudative (PSE), dark, firm, dry (DFD), and normal pork were stored under light or dark conditions at 4°C for 7 days. Sample pH, metmyoglobin reductase activity, oxygen consumption rate, and relative surface metmyoglobin and oxymyoglobin contents were determined. DFD pork had the highest metmyoglobin reductase activity and oxygen consumption rate. Enzyme activity of PSE was lower than that of normal pork, but no difference existed in oxygen consumption rate between PSE and normal samples. Metmyoglobin reductase activity dropped slowly during meat storage; oxygen consumption rate sharply decreased during the first day of storage. Both metmyoglobin reductase activity and oxygen consumption rate declined more rapidly in the light. Results can help develop guidelines for display and packaging of pork.     

皮质醇激素和血液生化指标变化对猪肉劣质肉的指示作用

为寻找猪肉劣质肉的指示指标,比较了不同质量猪肉对应皮质醇激素和血液生化指标的变化。结果表明,劣质肉中白肌肉(PSE)对应生猪血糖浓度显著高于正常肉(RFN)(P<0.05),劣质肉中黑干肉(DFD)对应生猪皮质醇浓度显著高于RFN肉(P<0.05)。说明血糖可作为劣质肉中PSE肉的重要指示指标,当宰前血糖浓度达到(17.21±3.12)mol/L时,可能产PSE肉;皮质醇可作为劣质肉中DFD肉的重要指示指标,当宰前皮质醇浓度达到(512.70±49.9)nmol/L时,可能产生DFD肉。     

The relationship of sarcoplasmic and myofibrillar protein solubility to colour and water-holding capacity in porcine longissimus muscle

In order to investigate the relationship of sarcoplasmic and myofibrillar protein solubility to colour and water-holding capacity (WHC) in pork, 60 loins were selected to represent the quality classes: PSE (pale, soft, exudative), RSE (reddish-pink, soft, exudative), RFN (reddish-pink, firm, non-exudative) and DFD (dark, firm, dry). PSE samples exhibited lower (p<0.05) protein solubility (sarcoplasmic, myofibrillar and total) compared to the other quality classes. RSE samples exhibited lower (p<0.05) sarcoplasmic protein solubility compared to DFD samples. RSE, RFN and DFD samples had similar myofibrillar and total protein solubilities. Sarcoplasmic protein solubility explained 71% of the variation in lightness with a linear decrease in L* value. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) gels of the sarcoplasmic and myofibrillar samples distinctly showed the association of some sarcoplasmic proteins with the myofibrillar protein fractions in PSE and RSE samples. The sarcoplasmic proteins which precipitated were phosphorylase, creatine kinase, triose phosphate isomerase and myokinase for PSE and phosphorylase for RSE samples. Pork colour is highly correlated with precipitation of sarcoplasmic proteins while WHC is affected by denaturation of myofibrillar proteins (PSE samples) and lower ultimate pH (PSE and RSE samples).     

Effect of Packaging on Color and Physical Characteristics of Ground Pork in Long-term Frozen Storage

Ground pork, 30% fat, was packaged in 454g units in Cryovac bags heat scaled under vacuum (V), Saran Wrap? (S), aluminum foil (A), Saran? overwrapped with aluminum foil (SA), and polyvinyl chloride (PVC) and frozen 13, 26, or 39 wk at ? 17°C. TBA values increased over time regardless of packaging. Those materials that excluded oxygen delayed lipid oxidation longest. Red color (CIE a* value and % reflectance difference at 630 and 580 nm) decreased over time; this was greater on exterior than interior of the meat block. Materials that excluded oxygen prevented loss of red color during the first 26 wk storage. Changes in redness and TBA appeared unrelated to pH. Changes in L* and b* values did not appear related to packaging treatment or storage time.     

CHEMICAL AND COLOR CHARACTERISTICS OF "LOMO EMBUCHADO" DURING SALTING SEASONING

"Lomo embuchado" is a traditional Spanish dry-cured meat product with two principal stages (salting-seasoning and dry-maturation) in its process. The evolution of chemical (moisture, nitrite, pH and lactic acid) and physical parameters: (CIELAB color space, chroma and hue, a*/b*, ΔE* and reflectance ratios R560/R500, R650/R570 and R630/RS80), during the salting-seasoning stage were measured. Three zones in the salted-seasoned loins were identified, and all parameters in each zone were analyzed. ANOVA and regression analyses were conducted. Moisture, pH and residual nitrite decreased with time (P<0.01), and lactic acid increased (P<0.05). Only moisture showed differences between zones (P<0.05). Color parameters changed during the salting-seasoning stage. Lightness (P<0.01), redness (only during the first 24 h (P<0.05)), and a*/b* ratio (P<0.01) increased. Yellowness (P<0.01), hue (P<0.01) and chroma (P<0.05) decreased during the process. The only parameter that was not affected by time and zone was reflectance ratio R630/R580 (P>0.05). Moisture and reflectance ratio R560/R500 were affected by zones (PCO.05). An excellent cured color was obtained during salting and seasoning.     

Effect of plant extracts on lipid oxidation during frozen storage of minced fish muscle

The aim of the study is to determine the effect of pomegranate seed extract (PSE) and grape seed extract (GSE) addition to chub mackerel minced muscle on lipid oxidation during frozen storage. Each extract was added to minced fish muscle at 2% concentration and then stored at ?18 °C for 3 months. The effect of plant dietary fibres to control lipid oxidation was compared with untreated samples (control). Formation of lipid hydroperoxides and thiobarbituric acid‐reactive substances (TBARS) was significantly inhibited by PSE and GSE addition when compared with control. Both extracts significantly retarded lipid oxidation according to the results of TBARS. A significant reduction of L* (lightness), a* (redness) and b* (yellowness) values was detected during frozen storage. GSE added samples had the highest redness and the lowest lightness and yellowness. However, samples with PSE showed the lowest redness and highest yellowness and h° (hue angle) values. The results from this study suggest GSE is a very effective inhibitor of primary and secondary oxidation products in minced fish muscle and have a potential as a natural antioxidant to control lipid oxidation during frozen storage of fatty fish.     

Effects of Endpoint Temperature on the Internal Color of Pork Loin Chops of Different Quality

ABSTRACT: The effects of 5 endpoint temperatures for cooked, internal color were determined for boneless pork longissimus muscle from 4 treatment groups: normal, normal-injected, PSE, and DFD. Visual and instrumental color, myoglobin denaturation, and acid phosphatase (ACP) of raw and cooked samples were evaluated. Visual internal color became (P < 0.05) less pink as endpoint temperature increased; however, DFD chops were more pink (P < 0.05) and PSE chops were less pink (P < 0.05) than other treatments at most endpoint temperatures. Cooked color was similar (P > 0.05) for chops from normal and normal-injected groups. Myoglobin denaturation increased as endpoint temperature increased. ACP activity in raw chops was not affected by treatment group and it was a good indicator of doneness at 71.1 °C.     

Measuring pork color: effects of bloom time, muscle, pH and relationship to instrumental parameters

To evaluate factors affecting pork color, the gluteus medius (GM), longissimus lumborumetthoracis (LT), semimembranosus (SM), biceps femoris (BF), and triceps brachii (TRI) muscles from pork carcasses of varying ultimate pHs were allowed to bloom for 30 min. L*, a*, and b* values, hue angle, chroma and visual color were determined. Color was evaluated using HunterLab (illuminants A, C, D(65) and F) and Minolta (illuminants C and D(65)) Spectrocolorimeters. LT had the highest L* value (51.31; TR=39.93) and hue angle (59.36; TR=46.94), and the lowest a* (7.52; TR=12.88) value. L* value was unaffected by bloom time; hue angle stabilized after 5 min, a* and b* values after 10 min and chroma after 20 min. Using the Minolta/illuminant D65, visual color best correlated with b* and L* values (r=-0.94 and -0.89) of LT. Using the Hunter/illuminant C, visual color correlated with L* value of LT, GM, BF and SM (r >-0.90 for each). Overall, the instrumental measure that best related to visual color was L* value.     

Effects of pork muscle quality on bacterial growth and retail case life

The effects of muscle quality (PSE, normal, DFD) upon the bacteriology and retail case life of pork chops were determined. Pork loin chops were processed from boneless backs after 90 days of frozen storage at -30°C. Variation in bacterial numbers was due to a highly significant (p < 0·001) storage time by muscle quality interaction. During simulated retail display, total psychrotrophs, Pseudomonas spp., Brochothrix thermosphacta and Enterobacteriaceae were lowest on PSE pork and highest on DFD pork in comparison to normal pork. Differences in bacterial densities were due to a longer lag phase in PSE pork and a shorter lag phase in DFD pork than in normal pork. Of the three muscle quality groups, DFD was most susceptible to the development of spoilage odours, while PSE pork was most sensitive to deterioration in appearance.     

PSE肉和DFD肉中糖原含量变化分析

利用蒽酮比色法进行检测正常肉、PSE肉和DFD肉中糖原含量的变化。糖原标液水解率为95.8%～98.7%,平均值为97.46%,相对标准偏差为1.25%。在0h,正常肉、PSE肉和DFD肉中糖原的平均含量分别为0.7560、0.7456、0.5284mg/g,RSD为0.3689%～0.7566%。PSE肉中糖原含量2h后下降到0.0420mg/g,RSD为2.3890%。正常肉和DFD肉的糖原含量在72h后分别下降到0.0608mg/g和0.0794mg/g,RSD为2.1445%和4.5931%。